A method for removing aluminum from lithium-containing acid leaching solution

Abstract

The present invention provides a method for removing aluminum from a lithium-containing acid leaching solution, and relates to the technical field of hydrometallurgy. The method comprises mixing the lithium-containing acid leaching solution with a strong alkaline solution to obtain a clear mixed solution without precipitate turbidity; adding a precipitant to the mixed solution and heating and stirring, stopping the addition of the precipitant after the pH reaches the target value, and continuing heating and stirring to obtain a solution containing a precipitate; filtering and separating the solution containing the precipitate to obtain a filtrate and a filter cake; washing and drying the filter cake to obtain aluminum hydroxide solid. The present invention can reduce the lithium loss rate to less than 5% and increase the aluminum removal rate to more than 99% by adjusting the pH of the acid leaching solution twice and optimizing the process parameters; the overall process steps are simple, the operation is convenient, the processing cycle is short, and it is easy to control, and the filtering performance is efficient, which is conducive to large-scale industrial production and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a method for removing aluminum from a lithium-containing acid leaching solution. Background Art

[0002] As the lightest metal element, lithium has a high redox potential and heat capacity. These characteristics make lithium a very special element that can be used in aviation, energy, medicine, industry and 3C electronic products. In recent years, the popularity of electric vehicles and the explosive development of portable smart devices have significantly increased the demand for lithium resources. The natural reserves of lithium are mainly found in ores, seawater, salt lake brine, etc., and lithium can be extracted and utilized through special means.

[0003] At present, for common lithium resources such as lithium ore and waste lithium batteries, whether directly through acid solution pressurization, atmospheric pressure leaching, or roasting-acid leaching, if the lithium-containing material has a high aluminum content, aluminum ions will inevitably enter the solution. When the conventional means are used to adjust the pH to remove impurities, the aluminum ions will be precipitated into the slag phase as aluminum hydroxide. Due to the large density and strong adsorption of aluminum hydroxide, lithium ions are easily adsorbed during the precipitation process, and the loss of lithium is 30-80%, which undoubtedly reduces the lithium recovery rate. In addition, the sodium hydroxide generated by this method is colloidal, not easy to flocculate, slow in filtration rate, poor in filtration performance, and increased production costs.

[0004] For example, Chinese patent CN109573974A discloses a method for removing aluminum from an acidic leachate in the recovery of waste lithium iron phosphate batteries. The method requires adding ammonium carbonate or ammonium bicarbonate to an acidic leachate with a pH of about 0.5 so that the solution pH is 2-3.5, and aluminum ions form a filter residue in the form of an iron-aluminum co-precipitate, and the filtrate is directly used to prepare battery-grade iron phosphate; obviously, the composition of the precipitate and the purpose of the filtrate are different, but iron hydroxide will adsorb lithium ions, resulting in a low recovery rate of lithium ions, and the purity of the precipitate is not high, and subsequent processing is relatively complicated.

[0005] Chinese patent CN112310500A discloses a method for separating aluminum elements from waste lithium iron phosphate materials. The method is to add a complexing agent to the waste lithium iron phosphate acid leaching solution containing aluminum elements to carry out a complexing reaction; the anions in the complexing agent include fluoride ions; obviously, this method consumes a lot of fluoride ions, and the generated fluoroaluminate complex precipitate needs to be separated by ions if it is to be used.

[0006] Chinese patent CN113816353A discloses a method for removing aluminum from the acid leaching solution of waste lithium iron phosphate batteries by iron-aluminum co-precipitation. The method requires first oxidizing the acid leaching solution or adding trivalent iron ions to adjust the concentration of trivalent iron ions in the leaching solution, and then performing a co-precipitation reaction by controlling the pH and temperature conditions of the leaching solution to obtain an aluminum-iron co-precipitate and a dealuminized solution. The component of the aluminum-iron co-precipitate is aluminum-iron hydroxide, which absorbs lithium ions and affects the recycling of lithium ions.

[0007] Chinese patent CN110980776A discloses a highly efficient aluminum removal method for lithium salt production. The method is to adjust the pH to 7.5-8 to facilitate Al 3+ Aluminum hydroxide precipitate is formed, Al 3+ At a pH of 7.5-8, only aluminum hydroxide precipitate will be formed. However, the aluminum hydroxide precipitate generated at this time will adsorb a large amount of lithium ions, causing lithium loss, and the hydroxide precipitate has a complex composition and cannot be well utilized after recovery. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the current method for removing aluminum from lithium-containing acid leaching solution is to add a precipitant to the acid leaching solution to prepare a precipitate for removal. Since iron hydroxide and aluminum hydroxide precipitates will adsorb lithium ions, the recovery rate of lithium ions is reduced; and the fluoroaluminate complex precipitate obtained by adding a complexing agent needs to be ion separated before it can be effectively utilized; although some can form an iron-aluminum compound precipitate containing aluminum ions together with trivalent iron ions, phosphate ions and hydroxide ions in the leaching solution, the material composition of the obtained precipitate is relatively complex, and subsequent utilization and treatment are difficult.

[0009] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0010] A method for removing aluminum from a lithium-containing acid leaching solution, the method for removing aluminum from a lithium-containing acid leaching solution comprises the following steps:

[0011] S1. Adjust pH:

[0012] The lithium-containing acid leaching solution is mixed with a strong alkaline solution to obtain a clear mixed solution without precipitation or turbidity;

[0013] S2. Precipitation:

[0014] Add a precipitant to the mixed solution of S1 and heat and stir. When the pH reaches the target value, stop adding the precipitant and continue heating and stirring to obtain a solution containing a precipitate.

[0015] S3, Filtering:

[0016] The solution containing the precipitate of S2 is filtered and separated to obtain a filtrate and a filter cake;

[0017] S4, washing and drying:

[0018] The filter cake of S3 is washed and dried to obtain aluminum hydroxide solid.

[0019] Optionally, the lithium and aluminum concentrations of the lithium-containing acid leaching solution in S1 are between 0.3-4 g / L and 2-25 g / L, respectively.

[0020] Optionally, the strong alkaline solution in S1 is any one of sodium hydroxide and potassium hydroxide.

[0021] Optionally, the pH of the lithium-containing acid leaching solution mixed with the strong alkaline solution in S1 needs to be adjusted to 2.8-3.2.

[0022] Optionally, the precipitant in S2 is at least one of NaHCO3, NH4HCO3, KHCO3, Na2CO3, (NH4)2CO3, and K2CO3.

[0023] Optionally, the pH in S2 reaches a target value of 4.5-7.

[0024] Optionally, the stirring method in S2 is stirring with a magnetic stirrer, the stirring speed is 100-300 rpm, the heating stirring temperature is 30-80° C., the heating stirring temperature is continued at 30-80° C., and the time is 20-180 min.

[0025] Optionally, due to the presence of carbonate in S2, the precipitate will exist in the form of small crystal nuclei to generate small particles rather than aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by the colloid and improves the filtering performance; the particle size of the aluminum hydroxide particles is 5-50μm.

[0026] Optionally, the filtration separation in S3 is liquid-solid separation using vacuum filtration, the main cation of the filtrate is sodium, the filtrate can be used to further recover sodium, and the component of the filter cake is aluminum hydroxide.

[0027] Optionally, the washing method in the washing and drying in S4 is to wash twice with deionized water and then put it into a dryer for drying.

[0028] Optionally, the water content of the aluminum hydroxide solid in S4 is less than 0.5%, and the content of the aluminum hydroxide solid component is 95-99%.

[0029] Technical principle of the present invention:

[0030] In general, the neutralization method is widely used in industrial applications to remove Al in production processes, mainly due to the advantages of low cost, wide application range, and simple operation. However, the amount of Al(OH)3 precipitate formed during the neutralization process is relatively large, and the Al(OH)3 precipitate is a flocculent colloid, which is difficult to filter. At the same time, the Al(OH)3 precipitate will carry Li, resulting in a large loss of Li.

[0031] In the present invention, the pH is first adjusted to the critical value for the precipitation of aluminum hydroxide by adding sodium hydroxide solution, and then a carbonate precipitant is added to consume the H in the solution. + And generate CO2. The hydroxide generated at this time will produce crystal nuclei instead of colloid, and exist in the form of small particles, thus avoiding the adsorption of lithium. At this time, the loss rate of lithium drops from 30-80% to <5%, and the removal rate of aluminum reaches more than 99%. At the same time, since aluminum hydroxide is no longer in a colloidal state, the filtration performance is also greatly improved.

[0032] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0033] The above scheme, the present invention provides a method for removing aluminum from a lithium-containing acid leaching solution, which overcomes the technical defects of the current aluminum removal process in the lithium-containing acid leaching solution, such as the difficulty in filtration caused by the precipitation of Al(OH)3 as a flocculent colloid, and the large Li loss caused by the adsorption of Li by the Al(OH)3 precipitation.

[0034] The present invention strengthens the alkaline substance to adjust the pH value of the acid leaching solution so that the solution is just clear without precipitation turbidity, and then the precipitant added generates small particles of aluminum hydroxide, thereby avoiding the generation of colloidal aluminum hydroxide and the adsorption of lithium, and improving the filtering efficiency.

[0035] The present invention adjusts the pH value of the acid leaching solution twice, so that the small-particle aluminum hydroxide finally produced will not adsorb a large amount of lithium, and the lithium loss rate is reduced from 30-80% to less than 5%; at the same time, the small-particle aluminum hydroxide can increase the aluminum removal rate to more than 99% during the filtration process.

[0036] In the present invention, carbonate is added to the solution containing precipitate, and when the precipitate is generated, the precipitate exists in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by the colloid and improves the filtering performance; wherein the particle size of the aluminum hydroxide particles is 5-50μm.

[0037] The filtration separation time of the present invention is shortened by 80-95% compared with the filtration separation time of the conventional method of adjusting pH to generate aluminum hydroxide precipitation, the water content of the aluminum hydroxide solid is less than 0.5%, and the content of the aluminum hydroxide component is 95-99%.

[0038] In summary, compared with other traditional methods, the method of the present invention can reduce the lithium loss rate to less than 5% and increase the aluminum removal rate to more than 99% by adjusting the pH of the acid leaching solution twice and optimizing the process parameters; the overall process steps are simple, the operation is convenient, the processing cycle is short, and it is easy to control. The filtration performance is efficient, which is conducive to large-scale industrial production and popularization. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 This is the precipitation morphology when removing aluminum from lithium-containing acid leaching solution by adjusting pH using traditional sodium hydroxide;

[0041] Figure 2 In a method for removing aluminum from a lithium-containing acid leaching solution in Example 1 of the present invention, the pH is first adjusted with sodium hydroxide, and then sodium carbonate is added to remove aluminum. The precipitation morphology;

[0042] Figure 3 This is a morphology diagram of the precipitation when, in a method for removing aluminum from a lithium-containing acid leaching solution in Example 2 of the present invention, the pH is first adjusted with sodium hydroxide, and then sodium bicarbonate is added to remove aluminum;

[0043] Figure 4 This is a method for removing aluminum from a lithium-containing acid leaching solution in Example 6 of the present invention, in which the pH is first adjusted with sodium hydroxide and then ammonium bicarbonate is added to remove aluminum, and the precipitation morphology is shown. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] A method for removing aluminum from a lithium-containing acid leaching solution, the method for removing aluminum from a lithium-containing acid leaching solution comprises the following steps:

[0046] S1. Adjust pH:

[0047] The lithium-containing acid leaching solution is mixed with a strong alkaline solution to obtain a clear mixed solution without precipitation or turbidity;

[0048] S2. Precipitation:

[0049] Add a precipitant to the mixed solution of S1 and heat and stir. When the pH reaches the target value, stop adding the precipitant and continue heating and stirring to obtain a solution containing a precipitate.

[0050] S3, Filtering:

[0051] The solution containing the precipitate of S2 is filtered and separated to obtain a filtrate and a filter cake;

[0052] S4, washing and drying:

[0053] The filter cake of S3 is washed and dried to obtain a strongly alkaline solid having the same alkaline substance composition as that of the strongly alkaline solution of S1.

[0054] In particular, the lithium and aluminum concentrations of the lithium-containing acid leaching solution in S1 are between 0.3-4 g / L and 2-25 g / L, respectively.

[0055] Particularly, the strong alkaline solution in S1 is any one of sodium hydroxide and potassium hydroxide.

[0056] In particular, the pH of the lithium-containing acid leaching solution mixed with the strong alkaline solution in S1 needs to be adjusted to 2.8-3.2.

[0057] In particular, the precipitant in S2 is at least one of NaHCO3, NH4HCO3, KHCO3, Na2CO3, (NH4)2CO3, and K2CO3.

[0058] In particular, the pH in S2 reached a target value of 4.5-7.

[0059] Particularly, the stirring method in S2 is stirring with a magnetic stirrer, the stirring speed is 100-300 rpm, the heating stirring temperature is 30-80° C., the heating stirring temperature is continued at 30-80° C., and the time is 20-180 min.

[0060] In particular, due to the presence of carbonate in S2, the precipitate will exist in the form of small crystal nuclei to generate small particles rather than aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by the colloid and improves the filtration performance; the particle size of the aluminum hydroxide particles is 5-50μm.

[0061] In particular, the filtration separation in S3 is liquid-solid separation using vacuum filtration, the main cation of the filtrate is sodium, the filtrate can be used to further recover sodium, and the component of the filter cake is aluminum hydroxide.

[0062] Particularly, the washing method in the washing and drying in S4 is to wash twice with deionized water and then put into a dryer for drying.

[0063] In particular, the water content of aluminum hydroxide solid in S4 is less than 0.5%, and the content of aluminum hydroxide solid component is 95-99%.

[0064] Example 1

[0065] A method for removing aluminum from a lithium-containing acid leaching solution, wherein the concentrations of lithium and aluminum in the lithium-containing acid leaching solution are between 1.2 g / L and 10 g / L, respectively. The method for removing aluminum from the lithium-containing acid leaching solution comprises the following steps:

[0066] S1. Adjust pH:

[0067] The lithium-containing acid leaching solution is mixed with a sodium hydroxide solution. The pH of the lithium-containing acid leaching solution is adjusted to 3.0 to obtain a clear mixed solution without precipitation and turbidity.

[0068] S2. Precipitation:

[0069] Add precipitant Na2CO3 to the mixed solution of S1 and heat and stir. When the pH reaches the target value of 6.0, stop adding precipitant Na2CO3 and continue heating and stirring to obtain a solution containing precipitate. When the precipitate is generated, it will exist in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid. This greatly reduces the adsorption of lithium by the colloid and improves the filtration performance. The specific precipitate morphology is as follows: Figure 2 As shown; the average particle size of the small aluminum hydroxide particles is 12 μm; wherein, a magnetic stirrer is used for stirring, the stirring speed is 250 rpm, the heating stirring temperature is 50° C., the heating stirring temperature is continued at 50° C., and the time is 60 min;

[0070] The precipitate morphology of this example is similar to Figure 1 The precipitate morphology when directly using sodium hydroxide to adjust the pH to remove aluminum can be compared to the precipitate formed in the form of small particles rather than Figure 1 The colloidal state will help reduce the adsorption of lithium by aluminum hydroxide and improve the filtration performance;

[0071] S3, Filtering:

[0072] The solution containing the precipitate of S2 is filtered and separated, and vacuum filtration is used for liquid-solid separation. The main cation of the filtrate is sodium, and the filtrate can be used to further recover sodium. The composition of the filter cake is aluminum hydroxide;

[0073] S4, washing and drying:

[0074] The filter cake of S3 is washed and dried, washed twice with deionized water, and then placed in a dryer to dry to obtain aluminum hydroxide solid.

[0075] In this embodiment, the water content of the aluminum hydroxide solid is less than 0.3%, and the content of the aluminum hydroxide component is 98.6%.

[0076] Example 2

[0077] A method for removing aluminum from a lithium-containing acid leaching solution, wherein the concentrations of lithium and aluminum in the lithium-containing acid leaching solution are between 2.2 g / L and 16.2 g / L, respectively. The method for removing aluminum from the lithium-containing acid leaching solution comprises the following steps:

[0078] S1. Adjust pH:

[0079] The lithium-containing acid leaching solution is mixed with a sodium hydroxide solution. The pH of the lithium-containing acid leaching solution is adjusted to 3.0 to obtain a clear mixed solution without precipitation and turbidity.

[0080] S2. Precipitation:

[0081] Add precipitant NaHCO3 to the mixed solution of S1 and heat and stir. Stop adding precipitant NaHCO3 after the pH reaches the target value of 5.5, continue heating and stirring to obtain a solution containing precipitate. When the precipitate is generated, it will exist in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by the colloid and improves the filtration performance. The specific precipitate morphology is as follows: Figure 3 As shown; the average particle size of the small aluminum hydroxide particles is 16.8 μm; wherein, a magnetic stirrer is used for stirring, the stirring speed is 200 rpm, the heating and stirring temperature is 40° C., and the heating and stirring temperature is continued at 40° C. for 90 min;

[0082] The precipitate morphology of this example is similar to Figure 1 The precipitate morphology when directly using sodium hydroxide to adjust the pH to remove aluminum can be compared to the precipitate morphology shown in the figure. It can be found that the precipitate formed is small particles rather than Figure 1 The colloidal state will help reduce the adsorption of lithium by aluminum hydroxide and improve the filtration performance;

[0083] S3, Filtering:

[0084] The solution containing the precipitate of S2 is filtered and separated, and vacuum filtration is used for liquid-solid separation. The main cation of the filtrate is sodium, and the filtrate can be used to further recover sodium. The composition of the filter cake is aluminum hydroxide;

[0085] S4, washing and drying:

[0086] The filter cake of S3 is washed and dried, washed twice with deionized water, and then placed in a dryer to dry to obtain aluminum hydroxide solid.

[0087] In this embodiment, the water content of the aluminum hydroxide solid is less than 0.4%, and the content of the aluminum hydroxide component is 96.6%.

[0088] Example 3

[0089] A method for removing aluminum from a lithium-containing acid leaching solution, wherein the concentrations of lithium and aluminum in the lithium-containing acid leaching solution are between 1.6 g / L and 6.5 g / L, respectively. The method for removing aluminum from the lithium-containing acid leaching solution comprises the following steps:

[0090] S1. Adjust pH:

[0091] The lithium-containing acid leaching solution is mixed with a sodium hydroxide solution. The pH of the lithium-containing acid leaching solution is adjusted to 2.8 to obtain a clear mixed solution without precipitation and turbidity.

[0092] S2. Precipitation:

[0093] Add precipitant KHCO3 to the mixed solution of S1 and heat and stir. Stop adding precipitant KHCO3 after pH reaches the target value of 5.5, continue heating and stirring to obtain a solution containing precipitate. When precipitate is generated, it will exist in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by colloid and improves the filtration performance. The specific precipitate morphology is as follows: Figure 3 As shown; the average particle size of the small aluminum hydroxide particles is 21.8 μm; wherein, a magnetic stirrer is used for stirring, the stirring speed is 260 rpm, the heating stirring temperature is 60° C., the heating stirring temperature is continued at 60° C., and the time is 90 min;

[0094] S3, Filtering:

[0095] The solution containing the precipitate of S2 is filtered and separated, and vacuum filtration is used for liquid-solid separation. The main cation of the filtrate is sodium, and the filtrate can be used to further recover sodium. The composition of the filter cake is aluminum hydroxide;

[0096] S4, washing and drying:

[0097] The filter cake of S3 is washed and dried, washed twice with deionized water, and then placed in a dryer to dry to obtain aluminum hydroxide solid.

[0098] In this embodiment, the water content of aluminum hydroxide solid is less than 0.4%, and the content of aluminum hydroxide component is 98.6%.

[0099] Example 4

[0100] A method for removing aluminum from a lithium-containing acid leaching solution, wherein the concentrations of lithium and aluminum in the lithium-containing acid leaching solution are between 1.52 g / L and 10.2 g / L, respectively. The method for removing aluminum from the lithium-containing acid leaching solution comprises the following steps:

[0101] S1. Adjust pH:

[0102] The lithium-containing acid leaching solution is mixed with a sodium hydroxide solution. The pH of the lithium-containing acid leaching solution is adjusted to 3.08 to obtain a clear mixed solution without precipitation and turbidity.

[0103] S2. Precipitation:

[0104] A mixture of precipitants Na2CO3 and NaHCO3 was added to the mixed solution of S1 in a mass ratio of 1:1, and heated and stirred. After the pH reached the target value of 5.5, the addition of the precipitant was stopped, and heating and stirring were continued to obtain a solution containing a precipitate. When the precipitate was generated, the precipitate would exist in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid, which greatly reduced the adsorption of lithium by the colloid and improved the filtration performance. The average particle size of the small aluminum hydroxide particles was 18.8 μm. A magnetic stirrer was used for stirring, the stirring speed was 200 rpm, the heating and stirring temperature was 70°C, the heating and stirring temperature was continued at 70°C, and the time was 120 min.

[0105] S3, Filtering:

[0106] The solution containing the precipitate of S2 is filtered and separated, and vacuum filtration is used for liquid-solid separation. The main cation of the filtrate is sodium, and the filtrate can be used to further recover sodium. The composition of the filter cake is aluminum hydroxide;

[0107] S4, washing and drying:

[0108] The filter cake of S3 is washed and dried, washed twice with deionized water, and then placed in a dryer to dry to obtain aluminum hydroxide solid.

[0109] In this embodiment, the water content of aluminum hydroxide solid is less than 0.3%, and the content of aluminum hydroxide component is 97.5%.

[0110] Example 5

[0111] A method for removing aluminum from a lithium-containing acid leaching solution, wherein the concentrations of lithium and aluminum in the lithium-containing acid leaching solution are between 1.89 g / L and 8.2 g / L, respectively. The method for removing aluminum from the lithium-containing acid leaching solution comprises the following steps:

[0112] S1. Adjust pH:

[0113] The lithium-containing acid leaching solution is mixed with a sodium hydroxide solution. The pH of the lithium-containing acid leaching solution is adjusted to 2.95 to obtain a clear mixed solution without precipitation and turbidity.

[0114] S2. Precipitation:

[0115] Add precipitant NaHCO3 to the mixed solution of S1 and heat and stir. Stop adding precipitant after pH reaches the target value of 5.5, continue heating and stirring to obtain a solution containing precipitate. When precipitate is generated, it will exist in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by colloid and improves the filtering performance. The average particle size of small aluminum hydroxide particles is 32.8 μm. A magnetic stirrer is used for stirring, the stirring speed is 180 rpm, the heating and stirring temperature is 40°C, the heating and stirring temperature is continued at 40°C, and the time is 160 min.

[0116] The precipitate morphology of this example is similar to Figure 1 The precipitate morphology when directly using sodium hydroxide to adjust the pH to remove aluminum can be compared to the precipitate morphology shown in the figure. It can be found that the precipitate formed is small particles rather than Figure 1 The colloidal state will help reduce the adsorption of lithium by aluminum hydroxide and improve the filtration performance;

[0117] S3, Filtering:

[0118] The solution containing the precipitate of S2 is filtered and separated, and vacuum filtration is used for liquid-solid separation. The main cation of the filtrate is sodium, and the filtrate can be used to further recover sodium. The composition of the filter cake is aluminum hydroxide;

[0119] S4, washing and drying:

[0120] The filter cake of S3 is washed and dried, washed twice with deionized water, and then placed in a dryer to dry to obtain aluminum hydroxide solid.

[0121] In this embodiment, the water content of the aluminum hydroxide solid is less than 0.2%, and the content of the aluminum hydroxide component is 98.6%.

[0122] Example 6

[0123] A method for removing aluminum from a lithium-containing acid leaching solution, wherein the concentrations of lithium and aluminum in the lithium-containing acid leaching solution are between 1.2 g / L and 10.1 g / L, respectively. The method for removing aluminum from the lithium-containing acid leaching solution comprises the following steps:

[0124] S1. Adjust pH:

[0125] The lithium-containing acid leaching solution is mixed with a sodium hydroxide solution. The pH of the lithium-containing acid leaching solution is adjusted to 3.1 to obtain a clear mixed solution without precipitation and turbidity.

[0126] S2. Precipitation:

[0127] Add precipitant NH4HCO3 to the mixed solution of S1 and heat with stirring. Stop adding precipitant after pH reaches the target value of 5.5, continue heating and stirring to obtain a solution containing precipitate. When precipitate is generated, it will exist in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by colloid and improves the filtration performance. The average particle size of small aluminum hydroxide particles is 18.8μm, and the specific precipitation morphology is as follows: Figure 4 As shown; wherein, a magnetic stirrer is used for stirring, the stirring speed is 160rpm, the heating stirring temperature is 50°C, the heating stirring temperature is continued at 50°C, and the time is 100min;

[0128] S3, Filtering:

[0129] The solution containing the precipitate of S2 is filtered and separated, and vacuum filtration is used for liquid-solid separation. The main cation of the filtrate is sodium, and the filtrate can be used to further recover sodium. The composition of the filter cake is aluminum hydroxide;

[0130] S4, washing and drying:

[0131] The filter cake of S3 is washed and dried, washed twice with deionized water, and then placed in a dryer to dry to obtain aluminum hydroxide solid.

[0132] In this embodiment, the water content of the aluminum hydroxide solid is less than 0.2%, and the content of the aluminum hydroxide component is 97.3%.

[0133] The above scheme, the present invention provides a method for removing aluminum from a lithium-containing acid leaching solution, which overcomes the technical defects of the current aluminum removal process in the lithium-containing acid leaching solution, such as the difficulty in filtration caused by the precipitation of Al(OH)3 as a flocculent colloid, and the large Li loss caused by the adsorption of Li by the Al(OH)3 precipitation.

[0134] The present invention strengthens the alkaline substance to adjust the pH value of the acid leaching solution so that the solution is just clear without precipitation turbidity, and then the precipitant added generates small particles of aluminum hydroxide, thereby avoiding the generation of colloidal aluminum hydroxide and the adsorption of lithium, and improving the filtering efficiency.

[0135] The present invention adjusts the pH value of the acid leaching solution twice, so that the small-particle aluminum hydroxide finally produced will not adsorb a large amount of lithium, and the lithium loss rate is reduced from 30-80% to less than 5%; at the same time, the small-particle aluminum hydroxide can increase the aluminum removal rate to more than 99% during the filtration process.

[0136] In the present invention, carbonate is added to the solution containing precipitate, and when the precipitate is generated, the precipitate exists in the form of small crystal nuclei to generate small particles instead of aluminum hydroxide colloid, which greatly reduces the adsorption of lithium by the colloid and improves the filtering performance; wherein the particle size of the aluminum hydroxide particles is 5-50μm.

[0137] The filtration separation time of the present invention is shortened by 80-95% compared with the filtration separation time of the conventional method of adjusting pH to generate aluminum hydroxide precipitation, the water content of the aluminum hydroxide solid is less than 0.5%, and the content of the aluminum hydroxide component is 95-99%.

[0138] In summary, compared with other traditional methods, the method of the present invention can reduce the lithium loss rate to less than 5% and increase the aluminum removal rate to more than 99% by adjusting the pH of the acid leaching solution twice and optimizing the process parameters; the overall process steps are simple, the operation is convenient, the processing cycle is short, and it is easy to control. The filtration performance is efficient, which is conducive to large-scale industrial production and popularization.

[0139] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for removing aluminum from a lithium-containing acid leaching solution, characterized in that: The method for removing aluminum from a lithium-containing acid leaching solution comprises the following steps: S1. Adjust pH: The lithium-containing acid leaching solution is mixed with a strong alkaline solution, and the pH is adjusted to a critical value of 2.8-3.2 at which aluminum hydroxide begins to precipitate, to obtain a clear mixed solution without precipitation turbidity; S2. Precipitation: Add a precipitant to the mixed solution of S1 and heat and stir. Stop adding the precipitant after the pH reaches the target value of 4.5-7, and continue heating and stirring to obtain a solution containing a precipitate; the precipitant is at least one of NaHCO3, NH4HCO3, KHCO3, Na2CO3, (NH4)2CO3, and K2CO3; S3, Filtering: The solution containing the precipitate of S2 is filtered and separated to obtain a filtrate and a filter cake; S4, washing and drying: The filter cake of S3 is washed and dried to obtain aluminum hydroxide solid.

2. The method for removing aluminum from a lithium-containing acid leaching solution according to claim 1, characterized in that: The lithium and aluminum concentrations of the lithium-containing acid leaching solution in S1 are between 0.3-4 g / L and 2-25 g / L, respectively.

3. The method for removing aluminum from a lithium-containing acid leaching solution according to claim 1, characterized in that: The strong alkaline solution in S1 is any one of sodium hydroxide and potassium hydroxide.

4. The method for removing aluminum from a lithium-containing acid leaching solution according to claim 1, characterized in that: The stirring method in S2 is to use a magnetic stirrer for stirring, the stirring speed is 100-300 rpm, the heating stirring temperature is 30-80° C., the heating stirring temperature is continued at 30-80° C., and the time is 20-180 min.

5. The method for removing aluminum from a lithium-containing acid leaching solution according to claim 1, characterized in that: The filtration separation in S3 adopts vacuum filtration, the main cation of the filtrate is sodium, the filtrate is used for further recovery of sodium, and the component of the filter cake is aluminum hydroxide.

6. The method for removing aluminum from a lithium-containing acid leaching solution according to claim 1, characterized in that: The washing method in the washing and drying in S4 is to wash twice with deionized water and then put it into a dryer for drying.

7. The method for removing aluminum from a lithium-containing acid leaching solution according to claim 1, characterized in that: The water content of aluminum hydroxide solid in S4 is less than 0.5%, and the content of aluminum hydroxide solid component is 95-99%.

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